U.S. patent number 10,584,906 [Application Number 15/808,837] was granted by the patent office on 2020-03-10 for refrigeration purge system.
This patent grant is currently assigned to CARRIER CORPORATION. The grantee listed for this patent is Carrier Corporation. Invention is credited to Haralambos Cordatos, Zissis A. Dardas, Yinshan Feng, Rajiv Ranjan, Michael A. Stark, Parmesh Verma, Georgios S. Zafiris.
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United States Patent |
10,584,906 |
Ranjan , et al. |
March 10, 2020 |
Refrigeration purge system
Abstract
Disclosed is a refrigeration system including a heat transfer
fluid circulation loop configured to allow a refrigerant to
circulate therethrough. A purge gas outlet is in operable
communication with the heat transfer fluid circulation loop. The
system also includes at least one gas permeable membrane having a
first side in operable communication with the purge gas outlet and
a second side. The membrane includes a porous inorganic material
with pores of a size to allow passage of contaminants through the
membrane and restrict passage of the refrigerant through the
membrane. The system also includes a permeate outlet in operable
communication with a second side of the membrane.
Inventors: |
Ranjan; Rajiv (South Windsor,
CT), Cordatos; Haralambos (Colchester, CT), Dardas;
Zissis A. (Worcester, MA), Zafiris; Georgios S.
(Glastonbury, CT), Feng; Yinshan (Manchester, CT), Verma;
Parmesh (South Windsor, CT), Stark; Michael A.
(Mooresville, NC) |
Applicant: |
Name |
City |
State |
Country |
Type |
Carrier Corporation |
Jupiter |
FL |
US |
|
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Assignee: |
CARRIER CORPORATION (Palm Beach
Gardens, FL)
|
Family
ID: |
61280445 |
Appl.
No.: |
15/808,837 |
Filed: |
November 9, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180066880 A1 |
Mar 8, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14909542 |
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9987568 |
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PCT/US2014/040795 |
Jun 4, 2014 |
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61864133 |
Aug 9, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D
53/22 (20130101); F25B 43/043 (20130101); B01D
19/0031 (20130101); F25B 43/003 (20130101); B01D
2311/103 (20130101) |
Current International
Class: |
F25B
43/04 (20060101); F25B 43/00 (20060101); B01D
19/00 (20060101); B01D 53/22 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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Apr 2006 |
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EP |
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EP |
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11248298 |
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5585307 |
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Sep 2014 |
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JP |
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Other References
European Search Report dated Mar. 14, 2019 cited in Application No.
18205247.2, 7 pgs. cited by applicant .
Chinese Office Action and Search Report from Chinese Patent Office
for CN Application No. 201480044756.4, dated Apr. 28, 2017, 17
pages, English Translation Included. cited by applicant .
Chinese Office Action and Search Report from Chinese Patent Office
for CN Application No. 201480044756.4, dated Dec. 14, 2017, 18
pages, English Translation Included. cited by applicant .
International Search Report for application PCT/US2014/040795,
dated Aug. 29, 2014, 4 pages. cited by applicant .
Written Opinion for application PCT/US2014/040795, dated Aug. 29,
2014, 4 pages. cited by applicant .
Coronas et al., "Separations Using Zeolite Membranes", Separation
and Purification Methods, vol. 28, 1999--Issue 2, Abstract Only, 6
pages. cited by applicant .
Rao et al., "Nanoporous carbon membranes for separation of gas
mixtures by selective surface flow", Journal of Membrane Science,
vol. 85, Issue 3, Dec. 2, 1993, pp. 253-264, Abstract Only, 3
pages. cited by applicant .
Battelle Memorial Institute, "Cascade Reverse Osmosis and the
Absorption Osmosis Cycle", ARPA-E,
http://arpa-e.energy.gov/?q=slick-sheet-project/cascade-reverse-osmosis-a-
ir-conditioning-system, release date Jul. 12, 2010, 1 page. cited
by applicant.
|
Primary Examiner: Greene; Jason M
Attorney, Agent or Firm: Cantor Colburn LLP
Parent Case Text
This is a continuation-in-part of U.S. patent application Ser. No.
14/909,542, which is a national stage of PCT/US2014/040795, which
claims priority to U.S. application Ser. No. 61/864,133, the
disclosures of each of which is incorporated herein by reference in
its entirety.
Claims
What is claimed is:
1. A refrigeration system comprising: a heat transfer fluid
circulation loop configured to allow a refrigerant to circulate
therethrough; a purge gas outlet in operable communication with the
heat transfer fluid circulation loop; at least one gas permeable
membrane having a first side in operable communication with the
purge gas outlet and a second side, said membrane comprising a
porous inorganic material with pores of a size to allow passage of
contaminants through the membrane and restrict passage of the
refrigerant through the membrane; a permeate outlet in operable
communication with the second side of the membrane; and a heat
source in controllable thermal communication with the membrane.
2. The refrigeration system of claim 1, further comprising a prime
mover operably coupled to the permeate outlet, the prime mover
configured to move gas from the second side of the membrane to an
exhaust port leading outside the fluid circulation loop.
3. The refrigeration system of claim 1, wherein the heat transfer
fluid circulation loop comprises a compressor, a heat rejection
heat exchanger, an expansion device, and a heat absorption heat
exchanger, connected together in order by conduit; wherein the
purge gas outlet is in operable communication with at least one of
the heat rejection heat exchanger, the heat absorption heat
exchanger and the membrane.
4. The refrigeration system of claim 1, further comprising a
retentate return conduit operably coupling the first side of the
membrane to the fluid circulation loop.
5. The refrigeration system of claim 2, wherein the prime mover
comprises a vacuum pump.
6. The refrigeration system of claim 1, further comprising a purge
gas collector operably coupled to the purge outlet and the
membrane.
7. The refrigeration system of claim 6, wherein the purge gas
collector comprises purge gas therein comprising refrigerant gas
and contaminants, said purge gas in a stratified configuration with
a higher concentration of refrigerant toward the purge outlet and a
higher concentration of contaminants toward the membrane.
8. The refrigeration system of claim 6, further comprising a
chiller coil disposed in the purge gas collector, the coil in
operable communication with the fluid circulation loop.
9. The refrigeration system of claim 6, wherein the heat source is
further in controllable thermal communication with the purge gas
collector.
10. The refrigeration system of claim 1, wherein the membrane
comprises a ceramic.
11. The refrigeration system of claim 1, wherein the at least one
gas permeable membrane comprises a plurality of gas permeable
membranes; wherein the plurality of gas permeable membranes are
arranged in serial or parallel communication.
12. A refrigeration system, comprising: a heat transfer fluid
circulation loop configured to allow a refrigerant to circulate
therethrough; a purge gas outlet in operable communication with the
heat transfer fluid circulation loop; at least one gas permeable
membrane having a first side in operable communication with the
purge gas outlet and a second side, said membrane comprising a
porous inorganic material with pores of a size to allow passage of
contaminants through the membrane and restrict passage of the
refrigerant through the membrane; a permeate outlet in operable
communication with the second side of the membrane; a first prime
mover operably coupled to the permeate outlet, the prime mover
configured to move gas from the second side of the membrane to an
exhaust port leading outside the fluid circulation loop; and a
second prime mover configured to move permeate from the second side
of the membrane to the first side of the membrane.
13. The refrigeration system of claim 1, further comprising a
filter or a vortex separator between the purge outlet and the
membrane.
14. A refrigeration system, comprising: a heat transfer fluid
circulation loop configured to allow a refrigerant to circulate
therethrough; a purge gas outlet in operable communication with the
heat transfer fluid circulation loop; at least one gas permeable
membrane having a first side in operable communication with the
purge gas outlet and a second side, said membrane comprising a
porous inorganic material with pores of a size to allow passage of
contaminants through the membrane and restrict passage of the
refrigerant through the membrane; a permeate outlet in operable
communication with the second side of the membrane; a prime mover
operably coupled to the permeate outlet, the prime mover configured
to move gas from the second side of the membrane to an exhaust port
leading outside the fluid circulation loop; and a controller
configured to operate fluid circulation loop in response to a
cooling demand signal and to operate the prime mover in response to
a determination of contaminants in the fluid circulation loop.
15. A method of operating the refrigeration system of claim 14,
comprising circulating a refrigerant through the heat transfer
fluid circulation loop in response to a cooling demand signal, said
fluid circulation loop comprising a compressor, a heat rejection
side of a first heat exchanger, an expansion device, and the heat
absorption side of a second heat exchanger, connected together in
order by conduit under conditions in which the refrigerant is at a
pressure less than atmospheric pressure in at least a portion of
the fluid circulation loop; collecting purge gas comprising
contaminants from the purge gas outlet; and transferring the
contaminants across the permeable membrane with the prime
mover.
16. The method of claim 15, further comprising collecting the purge
gas in a purge gas collector between the purge gas outlet and the
membrane.
17. The method of claim 16, further comprising stratifying purge
gas in the purge gas collector with a higher concentration of
refrigerant toward the purge gas outlet and a higher concentration
of contaminants toward the membrane.
18. The method of claim 15, further comprising returning
refrigerant from the first side of the membrane to the fluid
circulation loop.
Description
BACKGROUND
This disclosure relates generally to chiller systems used in air
conditioning systems, and more particularly to a purge system for
removing contaminants from a refrigeration system.
Chiller systems such as those utilizing centrifugal compressors may
include sections that operate below atmospheric pressure. As a
result, leaks in the chiller system may draw air into the system,
contaminating the refrigerant. This contamination degrades the
performance of the chiller system. To address this problem,
existing low pressure chillers include a purge unit to remove
contamination. Existing purge units use a vapor compression cycle
to separate contaminant gas from the refrigerant. Existing purge
units are complicated and lose refrigerant in the process of
removing contamination.
BRIEF DESCRIPTION
Disclosed is a refrigeration system including a heat transfer fluid
circulation loop configured to allow a refrigerant to circulate
therethrough. A purge gas outlet is in operable communication with
the heat transfer fluid circulation loop. The system also includes
at least one gas permeable membrane having a first side in operable
communication with the purge gas outlet and a second side. The
membrane includes a porous inorganic material with pores of a size
to allow passage of contaminants through the membrane and restrict
passage of the refrigerant through the membrane. The system also
includes a permeate outlet in operable communication with a second
side of the membrane.
In some embodiments, the system further includes a prime mover
operably coupled to the permeate outlet, and the prime mover is
configured to move gas from the second side of the membrane to an
exhaust port leading outside the fluid circulation loop.
In any one or combination of the foregoing embodiments, the heat
transfer fluid circulation loop includes a compressor, a heat
rejection heat exchanger, an expansion device, and a heat
absorption heat exchanger, connected together in order by conduit,
and the purge gas outlet is in operable communication with at least
one of the heat rejection heat exchanger, the heat absorption heat
exchanger and the membrane.
In any one or combination of the foregoing embodiments, the system
further includes a retentate return conduit operably coupling the
first side of the membrane to the fluid circulation loop. In some
embodiments, the prime mover is a vacuum pump
In any one or combination of the foregoing embodiments, the system
further includes a purge gas collector operably coupled to the
purge outlet and the membrane.
In any one or combination of the foregoing embodiments, the purge
gas collector includes purge gas therein comprising refrigerant gas
and contaminants, said purge gas in a stratified configuration with
a higher concentration of refrigerant toward the purge outlet and a
higher concentration of contaminants toward the membrane.
In any one or combination of the foregoing embodiments, the system
further includes a chiller coil disposed in the purge gas
collector, the coil in operable communication with the fluid
circulation loop.
In any one or combination of the foregoing embodiments, the system
further includes a heat source, said heat source being in
controllable thermal communication with at least one of the
membrane and the purge gas collector.
In any one or combination of the foregoing embodiments, the system
further includes a heat source in controllable thermal
communication with either or both of the membrane or a purge gas
collector between the purge outlet and the membrane.
In any one or combination of the foregoing embodiments, the
membrane includes a ceramic.
In any one or combination of the foregoing embodiments, the at
least one gas permeable membrane includes a plurality of gas
permeable membranes; wherein the plurality of gas permeable
membranes are arranged in serial or parallel communication.
In any one or combination of the foregoing embodiments, the system
further includes a second prime mover conduit to move permeate from
the second side of the membrane to the first side of the
membrane.
In any one or combination of the foregoing embodiments, the system
further includes a filter or a vortex separator between the purge
outlet and the membrane.
In any one or combination of the foregoing embodiments, the system
further includes a controller configured to operate fluid
circulation loop in response to a cooling demand signal and to
operate the prime mover in response to a determination of
contaminants in the fluid circulation loop.
Also disclosed is a method of operating a refrigeration system,
including circulating a refrigerant through a vapor compression
heat transfer fluid circulation loop in response to a cooling
demand signal. The fluid circulation loop includes a heat rejection
side of a first heat exchanger, an expansion device, and the heat
absorption side of a second heat exchanger, connected together in
order by conduit under conditions in which the refrigerant is at a
pressure less than atmospheric pressure in at least a portion of
the fluid circulation loop. Purge gas including contaminants is
collected from a purge outlet in the fluid circulation loop and
transferred across a permeable membrane with a prime mover. The
membrane includes a porous inorganic material with pores of a size
to allow passage of the contaminants through the membrane and
restrict passage of the refrigerant through the membrane.
In some embodiments, the method further includes collecting the
purge gas in a purge gas collector between the purge outlet and the
membrane.
In any one or combination of the foregoing embodiments, the method
includes stratifying purge gas in the purge gas collector with a
higher concentration of refrigerant toward the purge outlet and a
higher concentration of contaminants toward the membrane.
In any one or combination of the foregoing embodiments, the method
further includes returning refrigerant from the first side of the
membrane to the fluid circulation loop.
BRIEF DESCRIPTION OF THE DRAWINGS
The following descriptions should not be considered limiting in any
way. With reference to the accompanying drawings, like elements are
numbered alike:
FIG. 1 is a schematic depiction of an example embodiment of a
membrane purge system for a refrigeration system;
FIG. 2 is a schematic depiction of a refrigeration system including
a vapor compression heat transfer refrigerant fluid circulation
loop;
FIG. 3 is schematic depiction of an example embodiment of a
membrane purge system with purge collector and relevant components
of a vapor compression heat transfer refrigerant fluid circulation
loop;
FIG. 4 is schematic depiction of an example embodiment of a purge
system and relevant components of a vapor compression heat transfer
refrigerant fluid circulation loop, with membrane unit retentate
directed to the system evaporator;
FIG. 5 is schematic depiction of another example embodiment of a
purge system and relevant components of a vapor compression heat
transfer refrigerant fluid circulation loop, with a cooling element
in a purge collector;
FIG. 6 is schematic depiction of another example embodiment of a
purge system and relevant components of a vapor compression heat
transfer refrigerant fluid circulation loop, with a centrifugal
separator;
FIG. 7 is schematic depiction of another example embodiment of a
purge system and relevant components of a vapor compression heat
transfer refrigerant fluid circulation loop, with a permeate
recycle;
FIG. 8 is a schematic depiction of another example embodiment of a
purge system and relevant components of a vapor compression heat
transfer refrigerant fluid circulation loop, with membrane units in
a cascade configuration; and
FIG. 9 is a schematic depiction of another example embodiment of a
purge system and relevant components of a vapor compression heat
transfer refrigerant fluid circulation loop, with a thermal prime
mover.
DETAILED DESCRIPTION
A detailed description of one or more embodiments of the disclosed
apparatus and method are presented herein by way of exemplification
and not limitation with reference to the Figures.
With reference now to FIG. 1, there is shown an example embodiment
of a purge system that can be connected to a heat transfer fluid
circulation loop such as the one shown in FIG. 2. As shown in FIG.
1, the purge system receives gas comprising refrigerant gas and
contaminants (e.g., nitrogen, oxygen, or water) from a
refrigerant-containing refrigeration system such as shown in FIG.
12 through a purge connection 52 to a membrane separator 54 on a
first side of a membrane 56. In some embodiments, the contaminants
can comprise a non-condensable gas such as components of
atmospheric air (e.g., nitrogen, oxygen). A prime mover such as a
vacuum pump 58 connected to the membrane separator 54 through
connection 60 provides a driving force to pass the contaminant
molecules through the membrane 56 and exit the system from a second
side of the membrane 56 through an outlet 58. In some embodiments,
the prime mover can be in the fluid loop, e.g., a refrigerant pump
or compressor. Refrigerant gas tends to remain on the first side of
the membrane 56 and can return to the fluid circulation loop
through connection 64. A controller 50, the operation of which is
described in more detail below, is in operable communication with
the refrigeration system components.
The membrane 56 includes a porous inorganic material. Examples of
porous inorganic materials can include ceramics such as metal
oxides or metal silicates, more specifically aluminosilicates
(e.g., Chabazite Framework (CHA) zeolite, Linde type A (LTA)
zeolite, porous carbon, porous glass, clays (e.g., Montmorillonite,
Halloysite). Porous inorganic materials can also include porous
metals such as platinum and nickel. Hybrid inorganic-organic
materials such as a metal organic framework (MOF) can also be used.
Other materials can be present in the membrane such as a carrier in
which a microporous material can be dispersed, which can be
included for structural or process considerations.
Metal organic framework materials are well-known in the art, and
comprise metal ions or clusters of metal ions coordinated to
organic ligands to form one-, two- or three-dimensional structures.
A metal-organic framework can be characterized as a coordination
network with organic ligands containing voids. The coordination
network can be characterized as a coordination compound extending,
through repeating coordination entities, in one dimension, but with
cross-links between two or more individual chains, loops, or
spiro-links, or a coordination compound extending through repeating
coordination entities in two or three dimensions. Coordination
compounds can include coordination polymers with repeating
coordination entities extending in one, two, or three dimensions.
Examples of organic ligands include but are not limited to
bidentate carboxylates (e.g., oxalic acid, succinic acid, phthalic
acid isomers, etc.), tridentate carboxylates (e.g., citric acid,
trimesic acid), azoles (e.g., 1,2,3-triazole), as well as other
known organic ligands. A wide variety of metals can be included in
a metal organic framework. Examples of specific metal organic
framework materials include but are not limited to zeolitic
imidazole framework (ZIF), HKUST-1.
In some embodiments, pore sizes can be characterized by a pore size
distribution with an average pore size from 2.5 .ANG. to 10.0
.ANG., and a pore size distribution of at least 0.1 .ANG.. In some
embodiments, the average pore size for the porous material can be
in a range with a lower end of 2.5 .ANG. to 4.0 .ANG. and an upper
end of 2.6 .ANG. to 10.0 .ANG.. A. In some embodiments, the average
pore size can be in a range having a lower end of 2.5 .ANG., 3.0
.ANG., 3.5 .ANG., and an upper end of 3.5 .ANG., 5.0 .ANG., or 6.0
.ANG.. These range endpoints can be independently combined to form
a number of different ranges, and all ranges for each possible
combination of range endpoints are hereby disclosed. Porosity of
the material can be in a range having a lower end of 5%, 10%, or
15%, and an upper end of 85%, 90%, or 95% (percentages by volume).
These range endpoints can be independently combined to form a
number of different ranges, and all ranges for each possible
combination of range endpoints are hereby disclosed.
The above microporous materials can be can be synthesized by
hydrothermal or solvothermal techniques (e.g., sol-gel) where
crystals are slowly grown from a solution. Templating for the
microstructure can be provided by a secondary building unit (SBU)
and the organic ligands. Alternate synthesis techniques are also
available, such as physical vapor deposition or chemical vapor
deposition, in which metal oxide precursor layers are deposited,
either as a primary microporous material, or as a precursor to an
MOF structure formed by exposure of the precursor layers to
sublimed ligand molecules to impart a phase transformation to an
MOF crystal lattice.
In some embodiments, the above-described membrane materials can
provide a technical effect of promoting separation of contaminants
(e.g., nitrogen, oxygen and/or water molecules) from refrigerant
gas, which is condensable. Other air-permeable materials, such as
porous or non-porous polymers can be subject to solvent interaction
with the matrix material, which can interfere with effective
separation. In some embodiments, the capabilities of the materials
described herein can provide a technical effect of promoting the
implementation of a various example embodiments of refrigeration
systems with purge, as described in more detail with reference to
the example embodiments below.
The membrane material can be self-supporting or it can be
supported, for example, as a layer on a porous support or
integrated with a matrix support material. In some embodiments,
thickness of a support for a supported membrane can range from 50
nm to 1000 nm, more specifically from 100 nm to 750 nm, and even
more specifically from 250 nm to 500 nm. In the case of tubular
membranes, fiber diameters can range from 100 nm to 2000 nm, and
fiber lengths can range from 0.2 m to 2 m.
In some embodiments, the microporous material can be deposited on a
support as particles in a powder or dispersed in a liquid carrier
using various techniques such as spray coating, dip coating,
solution casting, etc. The dispersion can contain various
additives, such as dispersing aids, rheology modifiers, etc.
Polymeric additives can be used; however, a polymer binder is not
needed, although a polymer binder can be included and in some
embodiments is included such as with a mixed matrix membrane
comprising a microporous inorganic material (e.g., microporous
ceramic particles) in an organic (e.g., organic polymer) matrix.
However, a polymer binder present in an amount sufficient to form a
contiguous polymer phase can provide passageways in the membrane
for larger molecules to bypass the molecular sieve particles.
Accordingly, in some embodiments a polymer binder is excluded. In
other embodiments, a polymer binder can be present in an amount
below that needed to form a contiguous polymer phase, such as
embodiments in which the membrane is in series with other membranes
that may be more restrictive. In some embodiments, particles of the
microporous material (e.g., particles with sizes of 0.01 .mu.m to
10 mm, or in some embodiments from 0.5 .mu.m to 10 .mu.m) can be
applied as a powder or dispersed in a liquid carrier (e.g., an
organic solvent or aqueous liquid carrier) and coated onto the
support followed by removal of the liquid. In some embodiments, the
application of solid particles of microporous material from a
liquid composition to the support surface can be assisted by
application of a pressure differential across the support. For
example a vacuum can be applied from the opposite side of the
support as the liquid composition comprising the solid microporous
particles to assist in application of the solid particles to the
surface of the support. A coated layer of microporous material can
be dried to remove residual solvent and optionally heated to fuse
the microporous particles together into a contiguous layer. Various
membrane structure configurations can be utilized, including but
not limited to flat or planar configurations, tubular
configurations, or spiral configurations. In some embodiments, the
membrane can include a protective polymer coating or can utilize or
can utilize backflow or heating to regenerate the membrane, as
disclosed in greater detail in U.S. patent application Ser. No.
15/808,837, entitled "Low Pressure Refrigeration System with
Membrane Purge", the disclosure of which is incorporated herein by
reference in its entirety.
In some embodiments, the microporous material can be configured as
nanoplatelets such as zeolite nanosheets. Zeolite nanosheet
particles can have thicknesses ranging from 2 to 50 nm, more
specifically 2 to 20 nm, and even more specifically from 2 nm to 10
nm. The mean diameter of the nanosheets can range from 50 nm to
5000 nm, more specifically from 100 nm to 2500 nm, and even more
specifically from 100 nm to 1000 nm. Mean diameter of an
irregularly-shaped tabular particle can be determined by
calculating the diameter of a circular-shaped tabular particle
having the same surface area in the x-y direction (i.e., along the
tabular planar surface) as the irregularly-shaped particle. Zeolite
such as zeolite nanosheets can be formed from any of various
zeolite structures, including but not limited to framework type
MFI, MWW, FER, LTA, FAU, and mixtures of the preceding with each
other or with other zeolite structures. In a more specific group of
exemplary embodiments, the zeolite such as zeolite nanosheets can
comprise zeolite structures selected from MFI, MWW, FER, LTA
framework type. Zeolite nanosheets can be prepared using known
techniques such as exfoliation of zeolite crystal structure
precursors. For example, MFI and MWW zeolite nanosheets can be
prepared by sonicating the layered precursors (multilamellar
silicalite-1 and ITQ-1, respectively) in solvent. Prior to
sonication, the zeolite layers can optionally be swollen, for
example with a combination of base and surfactant, and/or
melt-blending with polystyrene. The zeolite layered precursors are
typically prepared using conventional techniques for preparation of
microporous materials such as sol-gel methods.
The membrane purge shown in FIG. 1 can be used with various types
of refrigeration systems. One example system is a vapor compression
cycle refrigeration system, an example embodiment of which is shown
in FIG. 2. As shown in FIG. 2, a heat transfer fluid circulation
loop is shown in block diagram form in FIG. 2. As shown in FIG. 2,
a compressor 10 pressurizes heat transfer fluid in its gaseous
state, which both heats the fluid and provides pressure to
circulate it throughout the system. In some embodiments, the heat
transfer fluid, or refrigerant, comprises an organic compound. In
some embodiments, the refrigerant comprises a hydrocarbon or
substituted hydrocarbon. In some embodiments, the refrigerant
comprises a halogen-substituted hydrocarbon. In some embodiments,
the refrigerant comprises a fluoro-substituted or
chloro-fluoro-substituted hydrocarbon. The hot pressurized gaseous
heat transfer fluid exiting from the compressor 10 flows through
conduit 15 to a heat rejection heat exchanger such as condenser 20,
which functions as a heat exchanger to transfer heat from the heat
transfer fluid to the surrounding environment, resulting in
condensation of the hot gaseous heat transfer fluid to a
pressurized moderate temperature liquid. The liquid heat transfer
fluid exiting from the condenser 20 flows through conduit 25 to
expansion valve 30, where the pressure is reduced. The reduced
pressure liquid heat transfer fluid exiting the expansion valve 30
flows through conduit 35 to a heat absorption heat exchanger such
as evaporator 40, which functions as a heat exchanger to absorb
heat from the surrounding environment and boil the heat transfer
fluid. Gaseous heat transfer fluid exiting the evaporator 40 flows
through conduit 45 to the compressor 10, thus completing the heat
transfer fluid loop. The heat transfer system has the effect of
transferring heat from the environment surrounding the evaporator
40 to the environment surrounding the condenser 20. The
thermodynamic properties of the heat transfer fluid must allow it
to reach a high enough temperature when compressed so that it is
greater than the environment surrounding the condenser 20, allowing
heat to be transferred to the surrounding environment. The
thermodynamic properties of the heat transfer fluid must also have
a boiling point at its post-expansion pressure that allows the
temperature surrounding the evaporator 40 to provide heat to
vaporize the liquid heat transfer fluid.
With reference now to FIG. 3, there is shown an example embodiment
of a purge system connected to a vapor compression heat transfer
fluid circulation loop such as FIG. 2 (not all components of FIG. 2
shown). As shown in FIG. 3, a purge collector 66 receives purge gas
including refrigerant gas and contaminants (e.g., nitrogen, oxygen)
from a purge connection 52 connected to the condenser 20. The purge
gas is directed from the purge collector 66 to a first side of a
membrane 56 in a membrane separator 54. In some embodiments, the
membrane separator 54 and purge collector 66 can be integrated into
a single unit by disposing the membrane 56 at the outlet of the
purge collector 66. A prime mover such as a vacuum pump 58
connected to the membrane separator 54 provides a driving force to
pass the contaminant gas molecules through the membrane 56 and exit
the system from a second side of the membrane 56 through an outlet.
A controller 50 receives system data (e.g., pressure, temperature,
mass flow rates) and system or operator control (e.g., on/of,
receipt of cooling demand signal), and utilizes electronic control
components (e.g., a microprocessor) to control system components
such as various pumps, valves, switches.
In some embodiments, the connection of the purge connection 52 to
the condenser can be made at a high point of the condenser
structure. In some embodiments, the purge collector 66 can provide
a technical effect of promoting higher concentrations of
contaminants at the membrane separator 54, which can promote more
effective mass transfer and separation. This effect can occur
through a stratification of gas in the purge collector 66 in which
lighter contaminants concentrates toward the top of the purge
collector 66 and heavier refrigerant gas concentrates toward the
bottom of the purge collector 66. In some embodiments, the purge
collector 66 can be any kind of vessel or chamber with a volume or
cross-sectional open space to provide for collection of purge gas
and for a low gas velocity during operation of the purge system
vacuum pump 58 to promote stratification. Stratification can also
occur at any time when the purge system is not operating (including
during operation of the refrigeration system fluid circulation
loop), as the purge collector 66 remains in fluid communication
with the purge connection 52 with essentially stagnant gas in the
purge collector 66. Other embodiments can also be employed to
promote higher concentrations of contaminants at the membrane
separator 54, as discussed in more detail below.
In some embodiments, refrigerant from the first side of membrane 56
can be returned to the refrigerant fluid circulation loop. As shown
in FIG. 4, a connection 67 returns retentate gas from the first
side of membrane 56 to the refrigerant fluid circulation loop at
the evaporator 40, through a control device such as expansion valve
68 utilized to accommodate the pressure differential between the
first side of the membrane 56 (which is close to the pressure at
the condenser 20) and pressure at the evaporator 40. It should be
noted that the control device can control either or both flow
through or pressure drop across the control device, and expansion
valve 68 is shown as an integrated control device unit that
performs both functions for ease of illustration, but could be
separate components such as a control valve and an expansion
orifice. In some embodiments, utilization of a bypass refrigerant
return can provide a technical effect of promoting greater
concentrations of contaminants at the first side of membrane 56 by
removing gas at the membrane 56 that is concentrated with
refrigerant after removal of contaminant gas molecules through the
membrane 56, so that refrigerant-concentrated gas can be displaced
with gas from the purge collector 66 that has a higher
concentration of contaminants. The bypass 67 can also include a
control or shut-off valve, which can be integrated with an
expansion device (i.e., an expansion valve), as described in more
detail in U.S. patent application Ser. No. 62/584,012, the
disclosure of which is incorporated herein by reference in its
entirety. In alternative embodiments (not shown), the bypass
conduit 67 can return refrigerant-laden gas to a colder side of the
condenser 20 or inlet of the compressor 10, in which case an
expansion device may not be needed due to lower pressure
differential compared to that of a bypass return to the evaporator
40. In such as case, the connection 67 can utilize a control device
such as a control or shut-off valve 69 that does not provide gas
expansion.
As discussed above, in some embodiments gas stratification in the
purge collector 66 can provide a technical effect of promoting
higher concentrations of contaminants at the first side of the
membrane 56, which in turn can promote more effective mass transfer
to the membrane and more effective separation. FIGS. 5 and 6 show
schematic depictions of embodiments that can promote stratification
and/or delivery of higher concentrations of contaminants to the
membrane 56. As shown in FIG. 5, a cooling element such as a heat
exchange coil loop 70 in fluid communication with cold refrigerant
from the evaporator can be disposed in the purge collector 66 to
promote stratification through thermally-induced densification of
refrigerant gas and/or through condensation of refrigerant gas. As
shown in FIG. 6, a centrifugal separator 72 can promote
stratification in the purge collector 66 by directing relatively
dense refrigerant gas radially outward (from where it can be
directed downward or back to the refrigerant fluid flow loop) while
relatively less dense contaminant gases can flow upward through the
purge collector 66 and on to the membrane separator 54. Centrifugal
separators can utilize a vortex-inducing blade or other assembly at
an upstream of the separator and components (e.g., walls and
channels) disposed radially outward for collecting separated gas of
higher density.
In another example embodiment that can promote a higher relative
concentration of contaminants at the first side of the membrane 56,
FIG. 7 shows a permeate recycle 74 that directs a portion of the
contaminants on the second side of the membrane 56 back to the
first side of the membrane. Recycle 74 can include a conduit with a
pump (e.g., a Venturi-style pump using pressurized fluid from the
refrigerant fluid flow loop or a small mechanical pump).
The above embodiments are examples of specific embodiments, and
other variations and modifications may be made. For example, a
single membrane is depicted for ease of illustration in the
above-discussed Figures. However, multiple membranes (or membrane
separation units) can be utilized, either in cascaded or parallel
configurations. An example embodiment of a cascaded configuration
is schematically depicted in FIG. 8. As shown in FIG. 8, membrane
separation units 54a and 54b (with membranes 56a and 56b) are
disposed in a cascaded configuration in which permeate from the
separation unit 54a is fed to the first side of the second
separation unit 54b. Retentate from the first side of the membranes
56a and 56b is routed through connections 67a and 67b to the
refrigerant fluid circulation loop at the evaporator 40, with
expansion devices 68a and 68b utilized to accommodate the pressure
differential between the first side of membranes 56a and 56b (which
is close to the pressure at the condenser 20) and pressure at the
evaporator 40. Other variations for protection of the membrane
through a polymer layer or regenerative back-flush or heating
cycles are disclosed in U.S. patent application Ser. No.
62/584,073, the disclosure of which is incorporated herein by
reference in its entirety.
Other system variations can involve the prime mover. The
above-discussed example embodiments utilize a vacuum pump in
communication with the permeate side of the membrane, but other
prime movers can be utilized. As an alternative to mechanical
vacuum pumps such as a vane pump or reciprocating piston pump,
Venturi-style pumps can be used in which a flowing fluid (e.g.,
refrigerant flowing through the refrigerant fluid flow loop is
routed through a Venturi device in fluid communication with the
permeate side of the membrane to draw a vacuum on the permeate side
of the membrane. Another example embodiment of a prime mover is
shown in FIG. 9, in which a heat source 76 can be activated to heat
the gas in the purge collector 66 in conjunction with isolating the
purge collector from the condenser, such as with a shut-off valve
or check-valve to cause thermal expansion and thereby provide
motive force to drive gas to and through the membrane 56. The heat
source 76 (or a different heat source) can also be used to control
the membrane temperature during operation to achieve target
membrane performance characteristics, or to heat the membrane for
membrane regeneration.
As mentioned above, the system includes a controller such as
controller 50 for controlling the operation of the heat transfer
refrigerant flow loop and the purge system. A refrigeration or
chiller system controller can operate the refrigerant heat transfer
flow loop in response to a cooling demand signal, which can be
generated externally to the system by a master controller or can be
entered by a human operator. Some systems can be configured to
operate the flow loop continuously for extended periods. The
controller is configured to also operate the control device in the
retentate return conduit, or the prime mover, or both the control
device and the prime mover, in response to a purge signal. The
purge signal can be generated from various criteria. In some
embodiments, the purge signal can be in response to elapse of a
predetermined amount of time (e.g., simple passage of time, or
tracked operating hours) tracked by the controller circuitry. In
some embodiments, the purge signal can be in response to human
operator input. In some embodiments, the purge signal can be in
response to measured parameters of the refrigerant fluid flow loop,
such as a pressure sensor.
The term "about", if used, is intended to include the degree of
error associated with measurement of the particular quantity based
upon the equipment available at the time of filing the application.
For example, "about" can include a range of .+-.8% or 5%, or 2% of
a given value.
The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the present disclosure. As used herein, the singular forms "a",
"an" and "the" are intended to include the plural forms as well,
unless the context clearly indicates otherwise. It will be further
understood that the terms "comprises" and/or "comprising," when
used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, element components, and/or
groups thereof.
While the present disclosure has been described with reference to
an exemplary embodiment or embodiments, it will be understood by
those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without
departing from the scope of the present disclosure. In addition,
many modifications may be made to adapt a particular situation or
material to the teachings of the present disclosure without
departing from the essential scope thereof. Therefore, it is
intended that the present disclosure not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this present disclosure, but that the present
disclosure will include all embodiments falling within the scope of
the claims.
* * * * *
References